Tube made in a single piece by injection of a plastic material

ABSTRACT

The tube ( 1 ) comprises a bottom part ( 1   a ), open for introduction of a product, which is then closable, and a top part ( 1   b ) which has a through-hole ( 2 ) for passage and exit of the product from the tube. The bottom part ( 1   a ) is delimited by a lateral surface which exhibits a smaller thickness than a thickness of a lateral surface of the top part ( 1   b ) which delimits a remaining part of the tube ( 1 ). The top part ( 1   b ) comprises an opening ( 3 ), which is larger than the through-hole ( 2 ) and is arranged in a zone of the top part ( 1   b ) in which the through-hole ( 2 ) is to be located, in which opening a reducer ( 4 ) is sealingly fitted, and in which reducer ( 2 ) the through-hole ( 2 ) is afforded.

TECHNICAL FIELD

The invention relates to a tube made in a single piece, obtained byinjection of a plastic material.

BACKGROUND ART

For some time now plastic tubes have tended to replace the well-knownmetal tubes, usually destined to contain fluid products, such as forexample creams and cosmetic products in general, which are made of softmaterials so that the product in the tube can be squeezed out with aprevalently elastic deformation.

Known tubes usually comprise an open lower part for introduction of theproduct, which lower part is then closable after the product has beenintroduced. There is also an upper part which includes a hole forpassage of the product as it exits the tube. These tubes are made eitherby welding the upper part, generally obtained by injection moulding, toa drawn cylindrical tube, or directly pressing the whole tube by plasticinjection in a mould. The present invention relates specifically to thelatter type of tube.

Tubes made in this way are sent to the product manufacturers, who fillthe tubes by introducing the product from the open bottom part, thenweld the bottom part and then removably close the passage hole of thetop part using a cap which will enable the user to open the tube to dosethe product, and to reclose the tube before its next use. The closure ofthe passage hole is generally obtained either by a screw-cap screwed ona thread made at the position of the through-hole, or by a pressure-capwith a little spur, which sealingly fits on the through-hole. Theproduction of tubes in a single piece by injection of plastic materialinvolves, for the manufacturer, some problems due to the very smallthickness of the wall of the tube which can be obtained by injectionwithout there being any excessive production rejects. The thickness ofthe wall, in fact, cannot be less than about 0.6-0.65 millimetres.

A thicker tube wall would lead to problems for the user (the producer ofthe creamy product), especially with regard to closing up the bottom ofthe tube.

The main aim of the present invention is to obviate the above-describeddrawbacks by providing a tube obtained in a single piece by injection ofplastic material, which is easy to construct and to use.

A further aim of the present invention is to provide a tube which can bemade using moulds that can produce in large numbers withoutdeteriorating.

An advantage of the present invention is to obtain higherstandardisation of moulds used to realise the tubes.

A further aim of the present invention is to provide a simple solutionwhich is easy to put into practice.

These aims and advantages are achieved by the invention, as it ischaracterised in the appended claims.

DISCLOSURE OF INVENTION

Further characteristics and advantages of the present invention willbetter emerge from the detailed description that follows of someembodiments of the invention, illustrated purely by way of non-limitingexample in the accompanying figures of the drawings, in which:

FIG. 1 is a vertical elevation section of a first embodiment of the tubeof the invention;

FIG. 2 is an enlarged-scale illustration of a detail of FIG. 1, relatingto the bottom part of the tube;

FIG. 3 is an enlarged-scale illustration of a detail of FIG. 1, relatingto the upper part of the tube;

FIG. 4 is a section in vertical elevation of a further possibleembodiment of the upper part of the tube.

The tube 1 of the invention is made in a single piece by injection ofplastic material, generally a soft material such as, for example,polyethylene, in a specially-designed mould. In this case the term“single-piece” in relation to the tube means a tube that is made in asingle operation by injection moulding, with an open bottom side forsubsequent introduction of the product, and a top part, entirelyconformed during the moulding process, in which the product outlet holeis made or, as will be better described herein below, a hole is affordedto which a reducer can subsequently be applied to reduce the diameter ofthe hole according to the degree of fluidity of the product that thetube is destined to contain.

During the same moulding process a cap can be realised, for closing theoutlet hole; this cap, which is not actually a part of the tube, canalso be made as a separate part. The object of the invention relatesspecifically to single-piece tubes made by injection moulding of aplastic material, since though this technology offers undoubtedadvantages over others, it also involves precise problems which makeapplication thereof tricky; the solutions proposed by this invention areaimed at overcoming these difficulties which are inherent in thetechnology.

The tube of the invention comprises, as with known-type tubes, a bottompart 1 a which is open and through which, in the packaging plants of theproducts the tube is destined for, a product will be introduced; thebottom part 1 a of the tube is closable after the fluid product has beenintroduced, for example by heat-welding. The tube is also provided witha top part 1 b in which a through-hole 2 is afforded for dispensing ofthe product from the tube during use of the product by the final user.

The tube of the invention can be, as for example is illustrated in thedetail of FIG. 4, of a type comprising a threaded mouth 1 c, cylindricalin shape, on which a cap is screwed. In particular, the top part 1 b ofthe tube comprises a circular-section opening 3, which is larger thanthe through-hole 2 and concentric therewith. A reducer 4 is included,which is realised separately by moulding and using other known methods,which reducer 4 is conformed so as to sealingly engage in the opening 3;in this case the through-hole 2 is afforded in the reducer 4. Thereducer 4 can also be welded, for example by heat-welding, to theopening 3.

The reducer 4 has a very simple conformation and can be obtained usingelementary and inexpensive means; in particular, the reducer 4 comprisesa disc 4 b, affording the through-hole 2, which disc 4 b restssuperiorly on the threaded mouth when an external ring 4 a of thereducer 4 is fitted in the opening 3.

This realisation enables easy manufacturing of the tube by injection, asthe top part 1 b thereof has an opening 3 which, independently of thedesired diameter for the through-hole 2, has a diameter which permitsuse of very large-diameter plugs for the realisation of the opening 3(equal to the opening 3) which therefore do not have the-drawback causedby smaller-diameter plugs (equal to the through-hole 2). In this way,with a predetermined type of tube having a single internal volume, it ispossible to use standard moulds realising a standard through-hole 3, butcombine them with a selection of moulds for the reducers 4, which arevery simple and economical to make, for realising reducers 4 havingvarious dimensions of the through-hole 2. In this way aconsiderable-range of tubes can be manufactured at a very limited cost.Also, a film 5 is usually attached by heat-welding onto the top part ofthe disc 4 b in order to close off the through-hole 2; this film isdetached at first use of the tube and serves as a security seal for thetube contents.

The tube can also be, as for example is illustrated in FIGS. 1 and 3, ofa type comprising a pressure-fit cap 6 which is hinged to the body ofthe tube and made directly by injection together with the body of thetube, using the same material as for the tube body, or differentmaterial; in general a more rigid material is used, such as, forexample, polypropylene.

The cap 6 is provided with a spur 6 a which sealingly inserts into thethrough-hole 2 of the tube. In this case an opening 3 of greaterdiameter is made with respect to the passage of the through-hole 2, anda reducer 4 is provided, which comprises an annular crown 4 c that restson the internal wall of the top part of the tube when an external ring 4a of the reducer 4 fits in the opening 3. An internal ring, concentricto the external ring 4 a, is provided, for defining the through-hole 2and housing the spur 6 a.

The top part of the tube, from which the product contained in the tubeexits during use, can be made in any other shape, even if the typesindicated are those which afford easier manufacture of the tube in asingle injection of plastic material.

The lower part 1 a of the tube, in all realisations, is delimited by alateral surface which exhibits a smaller thickness than that of thelateral surface delimiting the remaining part of the tube. Inparticular, the less-thick lateral surface has in fact a variable lengthstarting from the bottom end of the tube, ranging from a few millimetresto 1-2 centimetres. As the lengths of these tubes are normally comprisedbetween a few centimetres and 15-20 centimetres, the part of lateralsurface which exhibits the lowest thickness is in fact about one-tenthof the total length of the tube.

To make an injection moulding in a single piece, the thicknesses of thetube wall must be at least 0.6-0.65 millimetres in order to prevent anunacceptable number of rejects during production. This thickness of thetube wall represents an obstacle for the tube users as it is difficult,or in any case time-consuming and laborious, to close the bottom of thetube. The tube has to be supplied open at the bottom to enable theproduct to be introduced into it.

According to the present invention, the bottom part 1 a of the tube ismade with a thickness comprised between 0.40 and 0.55 millimetres. Giventhe modest measurements of the thinnest part, there are no excessiveproblems during the injection stage, which there would be if the wholeof the lateral wall were of the same very limited thickness. Thelimited-thickness of the lower zone of the tube also enables, or atleast makes much easier, faster and safer, the tube closure operation.

The reduction of the thickness of the lateral surface of the lower zoneof the tube is preferably obtained by keeping the external diameter ofthe tube constant while increasing the internal diameter thereof.Obviously in the case of a slightly conical tube the internal diameterincrease in the thinner-section zone will be obtained with an internalconnection zone 10 having a much greater angle of conicity than that ofthe tube.

Obtaining the reduction in thickness in the lower part of the tube is avery easy operation, which requires only a few modifications to moulds,which can also be moulds already in existence; a technician can see tothese changes. Also, the suggested shape of this invention does notrequire undercuts, which can make extraction of the central part fromthe mould difficult.

The adoption of the simple solutions described herein enables theplastic injection technology to be used, with a consequent andconsiderable reduction in working costs while resulting in a betterproduct both aesthetically and in terms of functionability. The use ofthis technology, already known for these tubes, had not previously beenfruitfully utilised due to various drawbacks, all of which are obviatedby the present invention.

1. A tube (1) made in a single piece by injection of a plastic material,comprising a bottom part (1 a) which is open for introduction of aproduct, and closable after the introduction thereof, and a top part (1b) having a through-hole (2) for passage of a product in outlet from thetube (1), wherein the bottom part (1 a) of the tube (1) is delimited bya lateral surface being thinner than a lateral surface delimiting aremaining part of the tube.
 2. The tube of claim 1, wherein the thinnerlateral surface is variable in length, starting from a bottom end of thetube, according to an overall length of the tube, from a minimum of afew millimetres up 1 to 2 centimetres, and represents about a tenth of atotal length of the tube (1).
 3. The tube of claim 1, wherein thethinner lateral surface has a thickness which is comprised between 0.40and 0.55 millimetres (1 a).
 4. The tube of claim 1, wherein a reductionin thickness of the lateral surface of the bottom part of the tube isobtained by increasing an internal diameter of the tube.
 5. The tube ofclaim 1, wherein the top part (1 b) of the tube comprises an opening (3)which is larger than the through-hole (2) and is arranged in a zone ofthe top part (1 b) in which the through-hole (2) is to be made; itcomprises a reducer (4) in which the through-hole (2) is made, whichreducer (4) is conformed and arranged to sealingly fit into the opening(3).
 6. The tube of claim 5, wherein the opening (3) has a circularsection and is located on a plane which is perpendicular to an axis ofthe tube; the reducer (4) comprising an external ring (4 a) which fitsin the opening (3); the through-hole being located concentrically to theexternal ring (4 a)